Jerry Avins wrote:> John E. Hadstate wrote: > >> "Jerry Avins" <jya@ieee.org> wrote in message >> news:86GdnUq6PeRicjnfRVn-vQ@rcn.net... >> >> >>> Aren't all wire lines analog? >>> >> >> >> Aren't all computers analog? > > > Why do you keep pretending to be superficial? Anything to be contrary? > > Digital computers are digital; that's what makes them digital computers. > They use digital circuits which are in turn made -- tadaa! -- from > analog components. Your silly claim would have it that ships are made > not of steel, but of ore.You mean the aren't? Well well. I always thought core carriers were made from ore. :-) Steve
An intriguing story about undersampling
Started by ●June 5, 2005
Reply by ●June 7, 20052005-06-07
Reply by ●June 8, 20052005-06-08
On Sun, 05 Jun 2005 07:09:46 GMT, "erine" <erine@hotmail.com> wrote:>Read this astonishing story at >http://spazioscuola.altervista.org/UndersamplingAR/UndersamplingAR.htm >Here it is an excerpt: >A STORY ABOUT UNDERSAMPLING > >by Angelo Ricotta - Rome, Italy > >a.ricotta@isac.cnr.it > >ITALIAN VERSION > > > >In the article "Turning Nyquist upside down by undersampling" by Bonnie >Baker, EDN 12 May 2005, are reported the two formulae and to compute an >allowable sampling frequency for undersampling a bandpass signal. I was >surprised by that because I have been using the(Angelo's sad story snipped) Hi Angelo, Shame on those Burr-Brown & EDN knuckleheads. There is *NO* excusing their behavior. Their plagiarism was a very bad thing to do in our business. Many of us here on comp.dsp have had bad experiences with people plagiarizing our work. Weeks ago I saw the Bonnie Baker article and was a little surprised to see a "bandpass sampling" sample rate computation scheme (your method) that I had not seen before. I experimented with your method (comparing it with a method that I use to compute Fs) and your scheme sure seems to work just fine. So Angelo, "Good work". I think Bonnie Baker should be made aware of your story and she should tell the "real story" of the origin of the method she included in her article. Angelo, to try to "make up" for the way you were treated back in the 1990s, let me know if you'd like me to help you convince Ms. Baker to tell your story. (Not that I have any influence on Ms. Baker, but I'm willing to help if I can.) See Ya', [-Rick-]
Reply by ●June 8, 20052005-06-08
"Rick Lyons" <R.Lyons@_BOGUS_ieee.org> ha scritto nel messaggio news:42a6d305.1760199921@news.sf.sbcglobal.net...> On Sun, 05 Jun 2005 07:09:46 GMT, "erine" <erine@hotmail.com> wrote: > >>Read this astonishing story at >>http://spazioscuola.altervista.org/UndersamplingAR/UndersamplingAR.htm >>Here it is an excerpt: >>A STORY ABOUT UNDERSAMPLING >> >>by Angelo Ricotta - Rome, Italy >> >>a.ricotta@isac.cnr.it >> >>ITALIAN VERSION >> >> >> >>In the article "Turning Nyquist upside down by undersampling" by Bonnie >>Baker, EDN 12 May 2005, are reported the two formulae and to compute an >>allowable sampling frequency for undersampling a bandpass signal. I was >>surprised by that because I have been using the > (Angelo's sad story snipped) > > Hi Angelo, > > Shame on those Burr-Brown & EDN knuckleheads. > > There is *NO* excusing their behavior. > Their plagiarism was a very bad thing to do > in our business. > > Many of us here on comp.dsp have had > bad experiences with people plagiarizing > our work. > > Weeks ago I saw the Bonnie Baker article and was > a little surprised to see a "bandpass sampling" > sample rate computation scheme (your method) that I > had not seen before. > > I experimented with your method (comparing it with > a method that I use to compute Fs) and your > scheme sure seems to work just fine. > So Angelo, "Good work". > > I think Bonnie Baker should be made aware of your > story and she should tell the "real story" of the > origin of the method she included in her > article. > > Angelo, to try to "make up" for the way you were > treated back in the 1990s, let me know if you'd like > me to help you convince Ms. Baker to tell your story. > (Not that I have any influence on Ms. Baker, but I'm > willing to help if I can.) > > See Ya', > [-Rick-] >Thank you Rick for your kind support. Actually I have wrote to Joshua Israelsohn, the editor of EDN on Analog (on 20 May 2005) and to Bonnie Baker (on 30 May 2005) asking them to publish my article but they did not answer! I wrote also to Jennifer Huber (on 31 May 2005), managing Editor of circuitcellar.com, but the same no answer. Eventually I decided to publish the article on the newsgroups and in a site trying to spread it around. Here it is my last letter: Da: Angelo Ricotta Data: 05/31/05 15:20:54 A: jennifer.huber@circuitcellar.com Oggetto: Article Proposal Dear Jennifer Stimulated by a recent article on undersampling published on EDN, I thought it would be of interest for people working on signal processing area to read about an intriguing story concerning undersampling and that involved me in the past. The article is in the attachment. Let me know if it is of your interest. Yours sincerely Angelo Ricotta If you think you may help, try. You have my gratefulness for that. See you Angelo begin 666 ATTACH~1.GIF M1TE&.#EA&@`:`)$"`"A>OGW"_P```````"'Y! $```(`+ `````:`!H```)0 ME(^IR^T/XPE -FJ"QI93`'*05TWE0R;B5:[9R:2"S+[V#"\R';?^7</=7(K= ESV$$]H9'9"4Y>C(E&("F.0H80$J(56NR'+Z;G 6$%JO7Z@(`.P`` ` end
Reply by ●August 3, 20052005-08-03
On Mon, 06 Jun 2005 23:00:35 -0700, glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:>Jerry Avins wrote: > >(snip) > >> He was continuing a line of inquiry begun by Michael Pupin much earlier. >> Pupin explained rather well why the first "successful" transatlantic >> cable needed several minutes per bit. He elucidated phase velocity and >> dispersion, and why they mattered. Until the cable was laid, nobody even >> thought about it. >> http://www.geocities.com/neveyaakov/electro_science/pupin.html > >There was a story not so long ago about the design of the GPS system >almost not considering general relativity. In the end they made support >for it optional, but it quickly was determined that it needed to be on. > >-- glenWhat does it affect by turning it off? i.e., where does it cause errors? Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●August 3, 20052005-08-03
Eric Jacobsen wrote:> On Mon, 06 Jun 2005 23:00:35 -0700, glen herrmannsfeldt > <gah@ugcs.caltech.edu> wrote: > > >>Jerry Avins wrote: >> >>(snip) >> >> >>>He was continuing a line of inquiry begun by Michael Pupin much earlier. >>>Pupin explained rather well why the first "successful" transatlantic >>>cable needed several minutes per bit. He elucidated phase velocity and >>>dispersion, and why they mattered. Until the cable was laid, nobody even >>>thought about it. >>>http://www.geocities.com/neveyaakov/electro_science/pupin.html >> >>There was a story not so long ago about the design of the GPS system >>almost not considering general relativity. In the end they made support >>for it optional, but it quickly was determined that it needed to be on. >> >>-- glen > > > What does it affect by turning it off? i.e., where does it cause > errors?Doppler. When the photons fall to earth, they gain energy, increasing their frequency. Atomic clocks are well enough matched and stable enough to detect the frequency shift with a 100-foot tower. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 3, 20052005-08-03
On Tue, 07 Jun 2005 13:43:51 -0400, Jerry Avins <jya@ieee.org> wrote:>Eric Jacobsen wrote: >> On Mon, 06 Jun 2005 23:00:35 -0700, glen herrmannsfeldt >> <gah@ugcs.caltech.edu> wrote: >> >> >>>Jerry Avins wrote: >>> >>>(snip) >>> >>> >>>>He was continuing a line of inquiry begun by Michael Pupin much earlier. >>>>Pupin explained rather well why the first "successful" transatlantic >>>>cable needed several minutes per bit. He elucidated phase velocity and >>>>dispersion, and why they mattered. Until the cable was laid, nobody even >>>>thought about it. >>>>http://www.geocities.com/neveyaakov/electro_science/pupin.html >>> >>>There was a story not so long ago about the design of the GPS system >>>almost not considering general relativity. In the end they made support >>>for it optional, but it quickly was determined that it needed to be on. >>> >>>-- glen >> >> >> What does it affect by turning it off? i.e., where does it cause >> errors? > >Doppler. When the photons fall to earth, they gain energy, increasing >their frequency. Atomic clocks are well enough matched and stable enough >to detect the frequency shift with a 100-foot tower. > >JerryHmmm...I'm not making the connection of how that would affect the GPS system. Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●August 3, 20052005-08-03
Eric Jacobsen wrote:> On Tue, 07 Jun 2005 13:43:51 -0400, Jerry Avins <jya@ieee.org> wrote: > > >>Eric Jacobsen wrote: >> >>>On Mon, 06 Jun 2005 23:00:35 -0700, glen herrmannsfeldt >>><gah@ugcs.caltech.edu> wrote: >>> >>> >>> >>>>Jerry Avins wrote: >>>> >>>>(snip) >>>> >>>> >>>> >>>>>He was continuing a line of inquiry begun by Michael Pupin much earlier. >>>>>Pupin explained rather well why the first "successful" transatlantic >>>>>cable needed several minutes per bit. He elucidated phase velocity and >>>>>dispersion, and why they mattered. Until the cable was laid, nobody even >>>>>thought about it. >>>>>http://www.geocities.com/neveyaakov/electro_science/pupin.html >>>> >>>>There was a story not so long ago about the design of the GPS system >>>>almost not considering general relativity. In the end they made support >>>>for it optional, but it quickly was determined that it needed to be on. >>>> >>>>-- glen >>> >>> >>>What does it affect by turning it off? i.e., where does it cause >>>errors? >> >>Doppler. When the photons fall to earth, they gain energy, increasing >>their frequency. Atomic clocks are well enough matched and stable enough >>to detect the frequency shift with a 100-foot tower. >> >>Jerry > > > Hmmm...I'm not making the connection of how that would affect the GPS > system.I understand that they rely on Doppler shifts for certain measurements. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 3, 20052005-08-03
Jerry Avins <jya@ieee.org> writes:> Eric Jacobsen wrote: > > On Tue, 07 Jun 2005 13:43:51 -0400, Jerry Avins <jya@ieee.org> wrote: > > > > > >>Eric Jacobsen wrote: > >> > >>>On Mon, 06 Jun 2005 23:00:35 -0700, glen herrmannsfeldt > >>><gah@ugcs.caltech.edu> wrote: > >>> > >>> > >>> > >>>>Jerry Avins wrote: > >>>> > >>>>(snip) > >>>> > >>>> > >>>> > >>>>>He was continuing a line of inquiry begun by Michael Pupin much earlier. > >>>>>Pupin explained rather well why the first "successful" transatlantic > >>>>>cable needed several minutes per bit. He elucidated phase velocity and > >>>>>dispersion, and why they mattered. Until the cable was laid, nobody even > >>>>>thought about it. > >>>>>http://www.geocities.com/neveyaakov/electro_science/pupin.html > >>>> > >>>>There was a story not so long ago about the design of the GPS system > >>>>almost not considering general relativity. In the end they made support > >>>>for it optional, but it quickly was determined that it needed to be on. > >>>> > >>>>-- glen > >>> > >>> > >>>What does it affect by turning it off? i.e., where does it cause > >>>errors? > >> > >>Doppler. When the photons fall to earth, they gain energy, increasing > >>their frequency. Atomic clocks are well enough matched and stable enough > >>to detect the frequency shift with a 100-foot tower. > >> > >>Jerry > > > > > > Hmmm...I'm not making the connection of how that would affect the GPS > > system. > > I understand that they rely on Doppler shifts for certain measurements.I don't believe so. Here's my non-authoritative view on how GPS works: Basically, each satellite transmits a continuous stream of "I am satellite n, and the time is t". The GPS receiver is able to calculate the position of the satellite in space (it has an ephemeris, i.e. a table of the orbital motions of all the satellites) at the time of its transmission (xs,ys,zs). This gives one equation for the position and time of the receiver: (x-xs)^2 + (y-ys)^2 + (z-zs)^2 = c^2(t-ts)^2 where c = the speed of light If the GPS receiver is synchronized with 4 satellites, then it has four equations with four unknowns, and can solve for the position and current time at the receiver. With more than 4 satellites, some sort of least squares solution is calculated to reduce the average error. With only 3 satellites, a GPS receiver can use its presumed altitude above the WGS84 ellipsoid (approximating the earth's surface) to generate a fictitious fourth equation to get a solution. (I chose (x,y,z) for illustrative purposes; it probably uses a different coordinate system like spherical, or ellipsoidal?) So I believe it's speed of light delays that are used, not the Doppler effect. My guess is that relativistic corrections are needed to keep the atomic clocks in sync due to time dilation caused by the orbital velocity. After all, relativistic time dilation was verified in experiments with atomic clocks aboard aircraft, and the satellites are a lot faster. Scott -- Scott Hemphill hemphill@alumni.caltech.edu "This isn't flying. This is falling, with style." -- Buzz Lightyear
Reply by ●August 3, 20052005-08-03
On 07 Jun 2005 16:41:50 -0400, Scott Hemphill <hemphill@hemphills.net> wrote:>So I believe it's speed of light delays that are used, not the Doppler >effect. > >My guess is that relativistic corrections are needed to keep the atomic >clocks in sync due to time dilation caused by the orbital velocity. >After all, relativistic time dilation was verified in experiments with >atomic clocks aboard aircraft, and the satellites are a lot faster. > >ScottAh, that makes sense. Since the terrestrial receivers are expecting time information the atomic clocks in the moving satellites have to be calibrated for ground reference time rather than moving satellite reference time. Very interesting! Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●August 3, 20052005-08-03
Scott Hemphill wrote:> Jerry Avins <jya@ieee.org> writes: >> I understand that they rely on Doppler shifts for certain measurements. > > I don't believe so. Here's my non-authoritative view on how GPS works: > > Basically, each satellite transmits a continuous stream of "I am satellite > n, and the time is t". The GPS receiver is able to calculate the position > of the satellite in space (it has an ephemeris, i.e. a table of the > orbital motions of all the satellites) at the time of its transmission > (xs,ys,zs). This gives one equation for the position and time of the > receiver: > > (x-xs)^2 + (y-ys)^2 + (z-zs)^2 = c^2(t-ts)^2 > > where c = the speed of light > > If the GPS receiver is synchronized with 4 satellites, then it has four > equations with four unknowns, and can solve for the position and current > time at the receiver. With more than 4 satellites, some sort of least > squares solution is calculated to reduce the average error. With only > 3 satellites, a GPS receiver can use its presumed altitude above the > WGS84 ellipsoid (approximating the earth's surface) to generate a > fictitious fourth equation to get a solution. > > (I chose (x,y,z) for illustrative purposes; it probably uses a different > coordinate system like spherical, or ellipsoidal?) > > So I believe it's speed of light delays that are used, not the Doppler > effect. >It's both. Speed of light delays for position, as you described. The Doppler shift is used for velocity calculation. The (general) relativistic effect is an increase in frequency, equivalent to all satellites drifting slowly towards you. It's due to the fact that time passes slower inside the gravity well.> My guess is that relativistic corrections are needed to keep the atomic > clocks in sync due to time dilation caused by the orbital velocity. > After all, relativistic time dilation was verified in experiments with > atomic clocks aboard aircraft, and the satellites are a lot faster. > > ScottI'm not sure if special relativity applies in this case. The result is the opposite, the clocks on the SVs seem to go faster, not slower. Kind regards, Iwo
